Process for making cellulose fibrous sheet



United States Patent PROCESS FOR MAKING CELLULOSE FIBROUS SHEET ArthurD. Jordan, Jr., Moorestown, N.J., assignor to Rohm & Haas Company,Philadelphia, Pa., a corporation of Delaware No Drawing. ApplicationApril 9, 1956 Serial No. 576,810

7 Claims. (Cl. 162-166) This invention relates to a process fordeposition of polymeric materials on fibers and is particularlyconcerned with the deposition of an aqueous dispersion of awater-insoluble polymer on fibers, such as paper fibers, suspended inthe aqueous system by means of polyvalent metal salts, such as alum.

Heretofore, when alum or like polyvalent metal salt has been used tocoagulate a dispersed polymer on fibers within an aqueous suspensionthereof, the alum has generally been added after the introduction of thedispersed polymer into the fiber suspension or slurry. Because of theimpossibility of getting the alum to become adsorbed on the fibersurfaces before coagulation of the polymer is effected, the polymerparticles have the opportunity to form numerous large aggregates in theaqueous medium before adsorption occurs on a fiber. The result is asocalled irregular deposition of non-uniform character sometimes calleda grape-bunch effect. A similar problem arises when the alum isdissolved and uniformly distributed through the fiber suspension beforeadding the polymer dispersion. Attempts have been made to limitthe'amount of alum to that and only that which can be completelyadsorbed by the fibers so that the polymer particles can be onlydeposited or coagulated on the fiber surfaces. However, this control ofthe amount of alum requires extreme care and it has been found thatinsufiicient alum can be adsorbed exclusively on the fiber surfaceswhile suspended in the aqueous system to provide the necessarycoagulating power to completely deposit the dispersed polymer on thefibers unless relatively small proportions of polymer (on weight offiber) are used. Hence, the general practice has been to add additionalalum after the introduction of the polymer dispersion to exhaust thepolymer onto the fibers. It has also been suggested in US. Patent2,375,245 to precipitate a metal "hydrate, such as aluminum hydrate, onthe fiber to aid the subsequent deposition of a natural or syntheticrubber.

It has been found, however, that the action of the hydrate on thepolymer dispersion is relatively feeble and sheets obtained by thisprocedure frequently show little, if any, of such benefit as is normallyexpected of polymer deposition onthe fiber in the making of fibroussheets, espe cially paper or paperboard. Because of the difficultiesencountered with alum and the like, there have been -many suggestionsfor replacing the alum at least partly -with organic polymeric materialshaving a multiplicity "of cationic charges, but while these coagulantsare highly effective, they are nevertheless comparatively expensive.

In accordance with the present invention, an improved process isprovided for the use of a polyvalent metal salt, such as alum, for thedeposition of aqueous polymer dispersions on fibers in aqueoussuspension. The process provides better retention and more uniformdistribu- "tion' of poly'me'r on the fibers and sheets formed fromsuchfibers are more uniform and have better physical properties. Theprocess of the present invention involves the prelimnary treatment ofthe fibers with an aqueous 15% of the polyvalent metal salt. If desired,the concentration of the salt may be at the saturation point in theaqueous medium in which the fibers are suspended for the treatment.After thorough mixing and intermingling of the fibers in the solution ofthe polyvalent metal salt, the excess solution is removed, such as bystraining or filtering the slurry or suspension through a porous body,such as through a conventional wire screen used in the paper-makingindustry, which may be assisted by the conventional suction box.

The fibers are then rinsed rapidly to remove any loosely held polyvalentmetal salt carried on the surface of the fibers. Rinsing is effectedwith water, either soft or hard, but preferably the former, at anyconvenient temperature from about 15 C. to 40 C. This may be simplyaccomplished by spraying the Water on the fibers While they aresupported on a conventional paper-making screen or other foraminous orporous support. Removal of the rinse liquid may involve simple drainingor the latter may be aided by suction.

' After rinsing, the fibers are quickly dispersed, or suspended in waterquickly, preferably with the aid of agitation. The consistency may be aslow as 0.1% or as high as 6% by weight of fiber on the Weight of water.Preferably, the consistency is between 1% and 3%. As soon as the fibersare well-distributed in the liquid, the polymer ,dispersion is added andmixed into the fiber suspension in the proportion desired. This may befrom about 1% by weight of polymer to 150% by weight thereof on theweight of the fiber depending on the properties desired in The benefitsobtained by the procedure of the present invention are particularlyvaluable when the polymer is used in higher proportions from 10% andespecially from 25% up to 150% on the weight of fiber. The addition ispreferably accompanied :by suitable mixing action, such as by gentleagitation.

The prompt addition of the polymer dispersion to the freshly dispersedfibers serves to bring the polymer particles into contact with thepolyvalent metal ions on ithe fiber or in close proximity to itssurface. preparation of the fiber suspension and reasonably promptmixing of the polymer dispersion into the freshly prepared fibersuspension precludes the liberation of polyvalent Rapid metal ions intothe body of the liquid in sutficient con- *'centration to cause anyappreciable aggregation of cojagulated polymer particles therein apartfrom the fibers.

The polymer particles are deposited substantially uniformly andcompletely on the fiber surfaces.

After deposition of the polymer particles is complete, the fibers may beformed into a sheet on any suit-able equipment, such as on any of thevarious types of papermaking equipment including laboratory types havingsieves or screens for making handsheets as well as commercial machines,such as those using the typical Fourdrinier wire screen or perforatedrotating cylinders.

As the polyvalent metal salts, there may be used any water-soluble saltof a trivalent or tetravalent metal of "groups III, IV, V, and Vi of theperiodic table. Examples include the water-soluble sulfates, chlorides,nitrates, and so on of aluminum, titanium, zirconium, tin, vana dium,antimony, chromium, molybdenum. Simple salts 'may be used such asaluminum chloride, stannic chloride,

or aluminum sulfate. Basic salts may be used, such as Also, basic aluland frequently referred to as papermakers alum,'may

solution 'containing at least 10% and preferably at least 1 .be used.Also double salts, such as sodium zirconium silicate, or the alums, suchas sodium or potassium aluminum sulfate or the corresponding chromealums are suitable. From the standpoint of inexpensiveness availability,reliability and convenience, the common potassium alum or paperrnakersalum is preferred.

In producing fibrous products in accordance with my invention anysuitable type of fibrous material may be employed and when producing alight weight sheet part or all of the fibrous material used is generallyvegetable fiber, such as news fiber. However, cotton fibers, cottonlinters, wool and wood or rag fibers m well as asbestos or mineralfibers may be employed. The invention is particularly valuable for thepreparation of modified paper or paperboard sheets from cellulosicfibers in the form of bleached or unbleached wood pulps, includingsulfite, kraft, soda, semichemical, and groundwood pulps, as well as ragpulp, rope pulp, jute pulp, and the like. The pulp may be unbeaten,highly beaten or lightly beaten before the treatment.

The polymer dispersion used may comprise any waterinsoluble linearaddition polymer either of neutral character or of anionic character,that is, it may, but need not, contain carboxylic or sulfonic acidgroups either in acid form or in the form of a salt of ammonium, of analkali metal, such as sodium, potassium, or lithium, or of awater-soluble amine, such as trimethylamine, an alkyiolamine, such asmonoethanolamine, di-, or triethanolamine, morpholine, and so on. Thepolymer. may be any homopolymer or copolymer preferably obtained byemulsion polymerization of one or more of the followingmonoethylenically unsaturated monomers: esters of acrylic acid ormethacrylic acid and monohydric alcohols such as methyl, ethyl, butyl,octyl, dodecyl, cyclohexyl, cyanoethyl, aminoethyl, and the like; estersof itaconic acid and the above alcohols; esters from maleic, fumaric orcitraconic acids, and the above alcohols; vinyl esters of carboxylicacids such as acetic, propionic, butyric, and the like; vinyloxyalkylesters such as vinyloxyethyl acetate, etc; vinyl ethers such as ethylvinyl ether, butyl vinyl ether, octyl vinyl ether, hydroxyethyl vinylether, vinyloxyethoxyethanol, vinyloxypropoxyethanol; methacrylonitrileor acrylonitrile; acrylamide, or methacrylamide, and N-substitutedamides of these types; vinyl chloride, vinyl bromide, vinylidcnechloride, vinylidene fluoride, vinylidene cyanide, 1-chloro-1-fiuoroethylene, ethylene, styrene. These monomers may also be copolymerizedwith small amounts (from about 0.5 to 7.5% by weight of the totalmonomer mixture) of an acid, such as methacrylic acid, acrylic acid,itaconic acid, maleic acid, fumaric acid, and so on.

In the emulsion copolymerization either an anionic or a non-ionicemulsifying or dispersing agent, or a mixture thereof may be used. Whenthe polymer lacks anionic groups such as carboxyl or sulfonic acidgroups inacid or salt form, it is generally preferable, but notessential, that an anionic emulsifier be used as the entire dispersingagent or as a substantial part of it or that the amount of non-ionicemulsifier that is used as the sole emulsifier is limited so that thepolymer dispersion has limited stability toward polyvalent metal ions.

Examples of anionic emulsifiers that may be used include soaps of higherfatty acids having 12 to 18 carbon atoms, namely those of sodium,potassium, ammonium, or amines, such as those mentioned above inreference to the salts of the acidic copolymers; alkali metal higherfatty alcohol sulfates or sulfonates having 8 to 18 carbon atoms,alkyl-substituted aryl sulfonates in which the alkyl groups contain atleast a total of 8 carbon atoms, such as sodium t-octylphenylsulfonate.

The non-ionic emulsifiers or dispersing agents that may be used forpreparing the monomeric emulsions before copolymerization or dispersionsof the polymer after polymerization include the following:alkylphenoxypolyethoxyethanols having alkyl groups of about seven toeighteen carbon atoms and 6 to 60 or more oxyeth- -ylene units, such asheptylphenoxypolyethoxyethanols, oetylphenoxypolyethoxyethanols,methyloctylphenoxypoldecylphenoxypolyethoxyethanols, and the like;polyethoxyethanol derivatives of methylene linked alky'l phenols;

sulfur-containing agents such as those made by condensing 6 to 60 ormore moles of ethylene oxide with nonyl, dodecyl, tetradecyl, t-dodecyl,and the like mercaptans or with alkylthiophenols having alkyl groups ofsix to fifteen carbon atoms; ethylene oxide derivatives of longfchainedcarboxylic acids, such as lauric, myristic, palmitic, oleic, and thelike or mixtures of acids such as found in tall oil containing 6 to 60oxyethylene units per molecule; analogous ethylene oxide condensates oflong-chained alcohols, such as octyl, decyl, lauryl, or cetyl alcohols,ethylene oxide derivatives of etherified or esterified polyhydroxycompounds having a hydrophobic hydrocarbon chain, such as sorbitanmonostearate containing 6 to 60 oxyethylene units, etc.; blockcopolymers of ethylene oxide and propylene oxide comprising ahydrophobic propylene oxide section combined with one or morehydrophilic ethylene oxide sections.

The process of the present invention is adapted to produce papers andother fibrous products having increased strengths. The papers and feltsobtained may be used for making paper boards, paper bags of the singlewall or multi Wall type, backings for flooring such as linoleum, roofingfelts, waterproof or moisturevaporproof paper, paper or board containersor cartons for milk, butter, foods, etc., resin-impregnated laminatingpaper, abrasives composed of resin-impregnated paper coated withabrasive particles, moulded articles, premoulded articles, electricalinsulators, filter paper, heat-insulating paper, or loose masses ofunfelted and unmoulded impregnated cellulose stock used for air filters,dust filters, heat-insulation and the like. v

The following examples are illustrative of the invention, parts being byweight unless otherwise indicated:

EXAMPLE 1 (a) A mass of bleached sulfite pulp (3.44 parts dry weight)are soaked in about 270 parts of an aqueous 33% papermakers alumsolution for 15 minutes, drained, rinsed with water for 15 seconds,quickly redispersed in 200 parts of fresh water and promptly thereafter4.3 parts of an aqueous dispersion containing 40% by weight of anemulsion copolymerized poly(methyl acrylate), dispersed by about 0.07part of sodium lauryl sulfate, is added and mixed in. One minutethereafter, the pulp slurry is deposited as a sheet (designated sheet A)on a screen, which is then dried and subjected to a Mullen burst testand an MIT fold test. The weight of the sheet is given in grams per 100sq. in. of area and the test results are given in Table I following.

(b) The same weight of bleached sulfite pulp as in part (a) is dispersedin 200 parts of water and deposited as a sheet (sheet B) to provide atest control sheet containing no alum or polymer.

(c) The procedure of part (a) is repeated except the rinse is omitted.Sheet C thereby obtained is tested as before.

(d) The same weight of bleached sulfite pulp as in part (a) is dispersedin 200 parts of water, 4.3 parts of the same poly(rnethyl acrylate)dispersion is added and mixed in. Then 13.5 parts of an aqueous 33% paprmakers alum solution is added to provide an excess of alum over theamount equivalent to the emulsifier. After mixing one minute, a sheet(sheet D) is formed and tested as before.

Table 1 Sheet Wt, g./100 Mullen Burst, MIT Fold sq. in. lbs/sq. in.

yethoxyethanols, nonylphenoxypolyethoxyethanols, do- V The results inTable I show a marked improvement in sheet A obtained by the process ofthe present invention as compared to sheet D'obtained by the usualprocedure involving addition of the polymer prior to that of alum. SheetC shows the importance of the rinsing step in the procedure of thepresent invention.

EXAMPLE 2 (a) 3.5 parts of bleached sulfite pulp (dry) is soaked in 270parts of an aqueous 33% papermakers alum solution for 15 minutes,drained, rinsed 15 seconds with water, redispersed rapidly in 200 partsof water, and promptly thereafter about 4.37 parts of anaqueousdispersion containing about 40% by weight of an emulsion polymerizedpoly(methyl acrylate) dispersed by about 0.07 part of sodiumlaurylsulfateis added. One minute thereafter, the slurry is. sheeted, and thesheet (sheet E) is dried and tested for tensile strength, Mullen burst,edge tear, and MIT fold. See Table II.

'(b) 3.5 parts of the same bleached sulfite pulp are soaked in 200 partsof water for 15 minutes and then dispersed in the water. Then.4.37 partsof an aqueous dispersion containing about 40% by weight of an emulsionpolymerized poly(methyl acrylate) dispersed by about 0.07 part ofsodiumlauryl sulfate is added. After intimate mixture, 13.5 parts of anaqueous 33 papermakers alum solution is added and mixed in. After oneminute, theslurry is formed into sheet F, dried and tested. See tableII.

' 1 Table II Wt, g./100 Mullen Tensile, Edge Tear,

Sheet sq. in. Burst, 1bs./in. lbS./iIl. MIT Fold lbs/sq. in.

E 6. 2o 82 as 16.8 2,006 F ,5. 55 67. 28 15- 6 794 :11 Table 'II showsmarked improvement in sheets when made ,by ,the procedure of. thepresent invention.

EXAMPLE 3 The procedure of Example 2(a) is repeated substituting 9 partsof an aqueous dispersion containing about 40% of an emulsion polymerizedcopolymer of 60% acrylonitrile, 30% ethyl acrylate, and 10% butylmethacrylate using a non-ionic emulsifier consisting essentially oft-octylphenoxypolyethoxyethanol containing about 10 oxyethylene units.Excellent and uniform disposition of polymer on the fibers in the sheetis obtained.

EXAMPLE 4 The procedure of Example 2(a) is repeated with similar resultswhen unbleached kraft is substituted for the pulp therein. 7

EXAMPLE 5 The procedure of Example 2(a) is repeated replacing the alumsolution with a corresponding volume of a 15% potassium alum solution.Excellent deposition and distribution of the polymer on the fibers ofthe sheet are obtained.

EXAMPLE 6 The procedure of Example 2(a) is repeated replacing thepolymer dispersion with a dispersion containing the same weight of acopolymer of about 65% ethyl acrylate, about 33% of methyl methacrylateand about 2% of methacrylic acid dispersed by the same non-ionic agentas described in Example 1 (a). Similar results are obtained.

EXAMPLE 7 The procedure of Example (a) is repeated replacing the polymerdispersion with a dispersion containing the same weight of a copolymerof about 65% ethyl acrylate, about 33% of methyl methacrylate and about2% of methacrylic acid dispersed by a mixture of 0.03 part of 6 the samenon-ionic agent as described in Example 1(a) and 0.04 part of sodiumlauryl sulfate. Similar results are obtained.

It is to be understood that changes and variations may be made withoutdeparting from the spirit and scope of the invention as defined by theappended claims.

I claim:

1. A process for making fibrous sheets which comprises treatingcellulose fibers in an aqueous solution containing an aluminum saltdissolved therein, the resultant mixture of fibers and salt solutioncontaining at least 10% by weight of the aluminum salt, removing excess:solution from the fibers, rapidly rinsing the fibers with water, rapidlyredispersing the rinsed fibers in water to form a suspension thereofhaving a consistency of 0.1 to 6% by Weight of fibers on the weight ofWater, and then, promptly after redispersing the fibers, mixing into thefiber suspension an aqueous dispersion of a water-insoluble additionpolymer, in an amount from 1 to by weight of the polymer based on theweight of the fibers, to thereby deposit the polymer on the fibers, andthen forming a sheet from the resulting fiber suspension, the steps ofthe process prior to the aforesaid mixing step serving to providealuminum ions and anions of said salt on the fibers when the polymer ismixed into the fiber suspension.

2. A process for making fibrous sheets which comprises treatingcellulose fibers in an aqueous solution cont aining an aluminum saltdissolved therein, the resultant mixture of fibers and salt solutioncontaining at least 10% by weight of the aluminum salt, removing excesssolution from. the fibers, rapidly rinsing the fibers with water,rapidly redispersing the rinsed fibers in water to form a suspensionthereof having a consistency of 0.1 to 6% by weight of fibers based on'the weight of water, and then, promptly. after redispersing the fibers,mixing into the fiber suspension. an aqueousdispersion of awater-insoluble addition polymer, in an amount from 25 to 150% by weightof the polymer based on the weight of the fibers, to thereby deposit thepolymer on the fibers, and then forming a sheet from the resulting fibersuspension, the steps of the process prior to the aforesaid mixing stepserving to provide aluminum ions and anions of said salt on the fiberswhen the polymer is mixed into the fiber suspension.

3. A process for making fibrous sheets which comprises treatingcellulose fibers in an aqueous solution containing an aluminum saltdissolved therein, the resultant mixture of fibers and salt solutioncontaining at least 10% by weight of the aluminum salt, removing excesssolution from the fibers, rapidly rinsing the fibers with water, rapidlyredispersing the rinsed fibers in water to form a suspension thereofhaving a consistency of 0.1 to 6% by weight of fibers based on theweight of water, and then, promptly after redispersing the fibers,mixing into the fiber suspension an aqueous. dispersion of awater-insoluble addition polymer dispersed by a non-ionic dispersingagent to thereby deposit the polymer on the fibers, the amount ofpolymer being from 1 to 150% by weight, based on the weight of thefibers, and then forming a sheet from the resulting fiber suspension,the steps of the process prior to the aforesaid mixing step serving toprovide aluminum ions and anions of said salt on the fibers when thepolymer is mixed into the fiber suspension.

4. A process for making fibrous sheets which comprises treatingcellulose fibers in an aqueous solution containing an aluminum saltdissolved therein, the resultant mixture of fibers and salt solutioncontaining at least 10% by weight of the aluminum salt, removing excesssolution from the fibers, rapidly rinsing the fibers with water, rapidlyredispersing the rinsed fibers in water to form a suspension thereofhaving a consistency of 0.1 to 6% by weight of fibers based on theweight of Water, and then, promptly after redispersing the fibers,mixing into the fiber suspension an aqueous dispersion of awater-insoluble addition polymer dispersed by an anionic dispersingagent to thereby deposit the ,polyrner'on' the fib rs, the amount ofpolymer being from 1 to 150% by weigh based on the weight of the fibers,and then forming a sheet from the resulting fiber suspension, the stepsof the process prior to the aforesaid mixing step serving to pro videaluminum ions and anions of said salt on the fibers when the polymer ismixed into the fiber suspension.

5. A process for making fibrous sheets which comprises treatingcellulose fibers in an aqueous solution containing an aluminum saltdissolved therein, the resultant mixture of fibers and salt solutioncontaining at least 10% by Weight of the aluminum salt, removing excesssolution from the fibers, rapidly rinsing the fibers with water, rapidlyredispersing the rinsed fibers in water to form a suspension thereofhaving a consistency of 0.1 to 6% by weight of fibers based on theweight of water, and then, promptly after redispersing the fibers,mixing into the fiber suspension an aqueous dispersion of a water-insohl ble addition polymer dispersed by a mixture Of a nonionic and ananionic dispersing agent to thereby deposit the polymer on the fibers,the amount of polymer being from 1 to 150% by weight, based on theweight of the fibers, and then forming a sheet from the resulting fibersuspension, the steps of the process prior to the aforesaid mixing stepserving to provide aluminum ions and anions of said salt on the fiberswhen the polymer is mixed into the fiber suspension.

6. A process for making fibrous sheets which comprises treatingcellulose fibers in an aqueous solution containing an aluminum saltdissolved therein, the resultant mixture of fibers and salt solutioncontaining at least 10% by weight of the aluminum salt, removing excesssolution from the fibers, rapidly rinsing the fibers with water, rapidlyredispersing the rinsed fibers in water to form a suspension thereofhaving a consistency of 0.1 to 6% by weight of fibers based on theweight of water, and then, promptly after redispersing the fibers,mixing into the fiber suspension an aqueous dispersion of a water-insol-'uble addition polymer containing monomeric units selected from thegroup consisting of earboxylic acids, am-

m nium nd al l m t l salts t ereof and sal s he with wat -so am n sto he y depo th Po yme on the fibers, said polymer being dispersed in thedispersion by a non-ionic dispersing agent, the amount of poly mer mixedin being from 1 to by Weig t, on the weight of the fibers, and thenforming a sheet from the resulting fiber suspension, the steps of theprocess prior to the aforesaid mixing step serving to provide aluminumions and anions of said salt on the fibers when the polymer is mixedinto the fiber suspension.

7. A process for making fibrous sheets which comprises treatingcellulose fibers in an aqueous solution containing an aluminum saltdissolved therein, the resultant mixture of fibers and salt solutioncontaining at least 10% by weight of the aluminum salt, removing excesssolution from the fibers, rapidly rinsing the fiberswith water, rapidlyredispersing the rinsed fibers in water to form a suspension thereofhaving a consistency of 0.1 to 6% by Weight of fibers based on theweight of water, and then, promptly after redispersing the fibers,mixing into the fiber suspension an aqueous dispersion of awater-insoluble addition polymer containing monomeric units Se? lectedfrom the group consisting of carboxylic acids, am monium and alkalimetal salts thereof and salts thereof with water-soluble amines tothereby deposit the polymer on the fibers, said polymer being dispersedin the dispersion by a mixture of a non-ionic and an anionic dispersingagent, the amount of polymer mixed in being from 1 to 150% by weight,based on the weight of the fibers, and the steps of the process prior tothe aforesaid mixing step serving to provide aluminum ions and anions ofsaid salt on the fibers when the polymer is mixed into the fibersuspension. 7

2,613,190 Feigley Oct. 7, 1952 2,657,991 Walsh et Nov. 3, 1953

1. A PROCESS FOR MAKING FIBROUS SHEETS WHICH COMPRISES TREATINGCELLULOSE FIBERS IN AN AQUEOUS SOLUTION CONTAINING AN ALUMINUM SALTDISSOLVED THEREIN, THE RESULTANT MIXTURE OF FIBERS AND SALT SOLUTIONCONTAINING AT LEAST 10% BY WEIGHT OF THE ALUMINUM SALT, REMOVING EXCESSSOLUTION FROM THE FIBERS, RAPIDLY RINSING THE FIBERS WITH WATER RAPIDLYREDISPERSING THE RINSED FIBERS IN WATER TO FORM A SUSPENSION THEREOFHAVING A CONSISTENCY OF 0.1 TO 6% BY WEIGHT OF FIBERS ON THE WEIGHT OFWATER, AND THEN, PROMPTLY AFTER REDISPERSING THE FIBERS, MIXING INTO THEFIBER SUSPENSION AN AQUEOUS DISPERSION OF A WATER-INSOLUBLE ADDITIONPOLYMER, IN AN AMOUNT FROM 1 TO 150% BY WEIGHT OF THE POLYMER BASED ONTHE WEIGHT OF THE FIBERS, TO THEREBY DEPOSIT THE POLYMER ON THE FIBERS,AND THEN FORMING A SHEET FROM THE RESULTING FIBER SUSPENSION, THE STEPSOF THE PROCESS PRIOR TO THE AFORESAID MIXING STEP SERVING TO PROVIDEALUMINUM IONS AND ANIONS OF SAID SALT ON THE FIBERS WHEN THE POLYMER ISMIXED INTO THE FIBER SUSPENSION.